Field of the Invention
This patent is directed to a clutch mechanism between a leadscrew and an electric motor for driving the leadscrew. It is particularly useful for enabling the manual opening of sliding plug doors on a public transit vehicle, such as a passenger bus. Such sliding doors are driven to open and close by alternate rotation of the leadscrew.
Description of Related Art
Sliding plug doors for transit vehicles are described in detail in U.S. Pat. No. 6,032,416 entitled “Transit Vehicle Door” assigned to the same assignee as the present invention.
As can be understood from the above-referenced prior art patent, outside sliding plug doors on a transit vehicle are actuated by use of an electric motor coupled to a leadscrew and nut drive usually through a gearbox. The leadscrew and nut drive a door carriage mounted on a linear slide. The disadvantage of this system is that when the doors need to be opened manually, such as in an emergency, the motor and gearbox are not decoupled from the leadscrew. Therefore, the door or doors can only be back driven while forcing turning of the leadscrew. This requires a strong manually applied force.
It is an advantage according to this invention to provide a clutching mechanism inserted between the output of the electric motor and gearbox and the leadscrew facilitating the emergency manual opening of the sliding doors.